Conventionally, typical apparatuses of this type have included, for example, in the single wafer processing of wafers comprising the process technology of semiconductor device manufacturing, supply control apparatuses for process gasses which supply a special, high-purity process gas (a special material gas or a purge gas) to the interior of each processing chamber. Such supply control apparatuses for process gasses are provided with, as shown for example in FIG. 11: a controller 61; an electromagnetic valve assembly 62, which is provided with a plurality of electromagnetic valves 62A-62E, the valve units of which operate individually in accordance with control signals from the controller 61; air-operated valves 63A-63E, which are provided in correspondence with the plurality of electromagnetic valves 62A-62E, and which comprise a plurality of gas pressure operated valves, comprising a gas system assembly 63; a plurality of flexible air tubes 64a-64e, for guiding an operating gas (air), which flows in accordance with the open or closed state of the valve units of the plurality of electromagnetic valves 62A-62E, to the drive units of the air-operated valves 63A-63E; and a plurality of process gas supply sources 65a-65d, which are connected to the upstream side (the primary pressure side) of the main valve units of air-operated valves 63A-63E, respectively. In addition, a predetermined processing chamber 67 (or 68), comprising the unit to be processed, is connected to the downstream side (the secondary pressure side) of the main valve units of air-operated valves 63A-63E, via connecting pipes 66a -66e; a special gas (a desired process gas) is supplied to processing chamber 67 in accordance with the open or closed state of the main valve units of the air-operated valves 63A-63E.
In this case, the inner diameters of each air tube 64a-64e are set so as to be equal (having, for example, an inner diameter of 4 mm); however, as a result of the positioning of the air-operated valves 63A-63E, the length of these air tubes is simply set so as to be as short as possible in accordance with the distance separating the electromagnetic valves 62A-62E, and the air-operated valves 63A-63E corresponding thereto. Accordingly, it is commonly the case that the maximum length among the air tubes is on the level of 3 to 4 times that of the shortest length thereamong.
On the other hand, the open or closed state of the electromagnetic valves 62A-62E is chiefly controlled by means of a mechanism which is electrically operated, while air-operated valves 63A-63E are chiefly controlled by means of a mechanism which is mechanically operated; as a result, while the operating time of electromagnetic valves 62A-62E (that is to say, the time from the point at which the drive unit inputs a predetermined control signal to the point at which the open or closed state of the valve unit of the electromagnetic valve is switched) is normally on the order of milliseconds, while the operating time of air-operated valves 63A-63E (that is to say, the time from the point at which the open or closed state of the electromagnetic valve is switched to the point at which the opened or closed state of the main valve unit of the air-operated valve is switched) is on the order of 0.2-2.5 seconds.
The connecting pipes 66a-66e, which connect the main valve units of the air-operated valves 63A-63E and the processing chambers 67 and 68, are normally formed of corrosion-resistant materials (typically, stainless steel), since special material gasses are caused to flow therethrough; the shapes and positional relationships thereof differ in accordance with the method of the apparatus, and are constant. Furthermore, by way of caution, it should be said that FIG. 11 depicts the schematic structure of the electromagnetic valves, air-operated valves, and other peripheral structural members which are shown in the Figures attached to the present specification; as a result, the size relationships or positional relationships or the like of the members differ from those which are actually employed.
In such a supply control apparatus, electromagnetic valves 62A-62E are employed because the electrical control thereof is a simple matter, while air-operated valves 63A-63E are employed because they are advantageous in the handling of special material gasses. Accordingly, in addition to creating a structure in which two types of valves are employed, it becomes impossible to instantaneously (at least on the order of the operating time of the electromagnetic valves) conduct the switching of the unit to be processed of the process gas, and in addition, the lengths of the connecting pipes 66a-66e, and the lengths of the air tubes 64a-64e, vary, so that the time from the point at which a control signal is outputted from controller 61 to the point at which the individual process gasses flow into the predetermined processing chamber 67 (the gas supply operating time) varies according to the flow paths of the individual process gasses.
However, when the gas supply operating times vary depending on the flow path of the process gasses, as in the structure of the conventional technology described above, it is the case that, for example, when the switching of the supply of the unit to be processed of the process gas is conducted between a mode in which the distance separating the electromagnetic valve and the air-operated valve is long, and a mode in which this distance is short, a state is produced in which two types of process gasses are mixed, at least within a limited time period during this switching.
Concretely, in FIG. 11, in the state in which a process gas is supplied to a predetermined processing chamber 66 at a predetermined flow rate via connecting pipe 66c as a result of the operation of air-operated valve 63C via air tube 64c as a result of the opening of electromagnetic valve 62C, when switching is conducted to a state in which another process gas is supplied to the processing chamber 67 at a predetermined flow rate via connecting pipe 66a as a result of the opening of air-operated valve 63A via an air tube 64a, which is shorter than the air tube 64c, as a result of the opening of electromagnetic valve 62A, the other process gas is supplied in a mixed state at a point in time at which the first process gas is still being supplied to processing chamber 67. In this case, when the length of the connecting pipe 66a is shorter than that of the connecting pipe 66c, the mixed supply state of the process gas may become more pronounced.
In other words, even when highly accurate setting of the flow rates of the process gasses is conducted in advance, high purity processing cannot be conducted in the processing chamber at least during switching periods, and the product quality and yield is reduced to that extent. The use of a method in which the timing of the switching is controlled by means of the timer control of controller 61 in accordance with the state of the gas flow path of the process gasses has been considered as one means to avoid the mixed supply state of the process gasses described above; however, in such a method, the setting of the sequence of the timing is complicated, and as a result, such a method cannot be expected to result in the precise supply of process gasses.
The present invention was created in order to solve the problems present in the conventional technology described above; it has as an object thereof to provide a supply control apparatus for special gasses in which the operating time of the gas pressure operated valves activated after the operation of the electromagnetic valves can be easily controlled, and as a result, the timing of the switching of the supply states of the special gasses can be accurately conducted in accordance with the open or closed state of the gas pressure operated valves which operate in reaction to the electromagnetic valves which are operated in a time series.